EP0573453B1

EP0573453B1 - Device for alternately controlling two cooperating valves, especially safety valves on pressure vessels

Info

Publication number: EP0573453B1
Application number: EP92904263A
Authority: EP
Inventors: Bo Seborn
Original assignee: ARMATURJONSSON AB
Current assignee: ARMATURJONSSON AB
Priority date: 1991-01-28
Filing date: 1992-01-27
Publication date: 1995-11-08
Anticipated expiration: 2012-01-27
Also published as: SE9100238L; AU1204792A; WO1992013223A1; DE69205974T2; SE9100238D0; DE69205974D1; SE467799B; EP0573453A1

Abstract

A device for alternately controlling two cooperating valve assemblies (4, 6; 5, 7) comprises a connection tube (9) connected therebetween, and a movable lever (10) for moving and rotating a carrier element which is arranged in said tube (9) and which by means of said lever (10) is movable into coupling engagement with the spindles of the valves (4, 5), which are arranged in said tube (9) and directed towards one another. The control device (8) provides a normal position in which both valves (4, 5) are open, and two service positions in which one valve is open and the other is closed, and vice-versa. In addition, a guide means (23) prevents a state in which both valves (4, 5) are fully or partly closed. The device (8) is especially applicable to safety valves (6, 7) on pressure vessels (1).

Description

The present invention relates to controlling of cooperating valves, especially safety valves on pressure vessels, and more precisely to a control device of the type stated in the preamble of claim 1.
In most countries, strict safety regulations apply to pressure vessels containing inflammable liquids and gases under excess pressure. In Sweden, for example, the Pressure Vessel Commission has issued the publication "Tank Standardisation Rules III" of 1973, which stipulates on pp 14-18 that such pressure vessels must be provided with safety valves which should satisfy a number of requirements. These safety valves should open at a certain maximum pressure in the tank depending on the one hand on the strength of the tank and, on the other hand, on the type of gas contained therein. For conventional liquefied petroleum gas mixtures the opening pressure is about 1.5-2.0 MPa.
To make it possible to change, service or, for inspection, dismount such valves without safety being jeopardised, a pressure vessel of the above-mentioned type must be provided with two safety valves which are separately disconnectible and of which at least one should continuously be in its active, pressurised position. Between the two safety valves, a device should be arranged by means of which the valves can alternately be disconnected from the pressure. Alternatively, the safety valves are each mounted on a shut-off valve which in turn is arranged on the two outlets of the pressure vessel. The two shut-off valves are mechanically interconnected by a connection device and are usually operated by a lever. Irrespective of the device used, one valve outlet should be fully open when the other is closed, and it should not be possible to throttle the connection in the intermediate position. Examples of devices, in which shutting off is effected before safety means, are shown in "Tank Standardisation Rules III", p. 18, Fig. 6:2.
Ordinary ball valves are often used as shut-off valves. A prior-art device in double safety valves comprises two ball valves connected thereto, which can be rotated through 90° and are arranged with their valve spindles directed towards one another. The spindles are nonrotatably interconnected by means of a coupling rod which is rotatable by means of a lever. Since one ball valve is mounted in a position rotated 90° relative to the other, two positions are alternately provided as the lever is pivoted through 90° (by rotating the coupling rod) in either direction, viz. a first position in which the first valve is open and the second is closed, and a second position in which the first valve is closed and the second is open.
The legally responsible authorities have lately announced that the safety regulations for pressure vessels will be made more stringent. In Sweden, the regulations stated in "Tank Standardisation Rules III" still apply, but with certain complementary additions in the publication "Code of Statutes of the National Board of Occupational Safety and Health", AFS 1988:11, of 1988. The prior-art control devices for alternately disconnecting safety valves, which have been discussed above, will in future not satisfy the more and more stringent requirements. In fact, these control devices suffer from the obvious drawback that both safety valves cannot be in their active pressurised position at the same time, which would improve safety to a considerable extent. Moreover, there is a risk that both shut-off valves are partly open in the intermediate positions during reversing of the valves, which of course is a serious drawback.
A particular inconvenience caused by prior-art control devices is that the mechanical connection between the valves sets limits to the mutual positioning of the valves. For example, the valve spindles must in many cases be directed in a certain way to make it possible to provide an active mechanical connection between them.
One object of the present invention therefore is to obviate these drawbacks by providing a device for alternately controlling two cooperating valves, especially safety valves on pressure vessels, said device allowing both valves to be open in a normal position, and preventing both valves from being fully or partly open in an intermediate position.
A further object is to provide a control device by means of which the valves can easily be put in two different service positions, in which the first valve is fully closed and the second fully open, and vice versa.
One more object is to provide a control device which can be locked in the normal position and in the two service positions for preventing improper manipulation.
A still further object is to provide a control device consisting of a limited number of moving parts which can be operated in simple motions.
A special object is to provide a control device which allows more freedom of mounting the valves in optional positions relative to one another.
The invention further aims at providing a control device which is easily applicable to standard type valves which are adapted to be mounted on existing outlet fittings on pressure vessels.
According to the invention, these and other objects which will be apparent from the specification below have now been achieved by means of a control device which is of the type mentioned by way of introduction and moreover has the features stated in the characterising clause of claim 1. Preferred embodiments of the invention are stated in the subclaims.
The invention will now be described in more detail with reference to the accompanying drawings which illustrate some embodiments.
Fig. 1 is a side view of a control device according to a first embodiment of the invention, mounted between two valve assemblies on a pressure vessel.
Fig. 2 is a schematic perspective view of the control device according to the first embodiment of the invention.
Fig. 3 is a schematic view of the control device shown in Fig. 2, a connecting tube being removed for better clarity.
Fig. 4 is an axial view of a control device according to a second embodiment of the invention.
Fig. 5 is a perspective view of a valve spindle included in the control device illustrated in Fig. 4.
Figs 6 and 7 illustrate a control device according to a third embodiment of the invention.
Fig. 1 illustrates a portion of a pressure vessel 1 containing e.g. a liquefied petroleum gas mixture under excess pressure. The pressure vessel 1 comprises in prior-art manner two outlets in the form of two spaced-apart pipe connections 2, 3 on which two identical valve assemblies are mounted.
In a per se known manner, each valve assembly comprises a shut-off valve 4, 5 and a safety valve 6, 7 mounted thereon. All valves 4-7 are standard type valves. As shut-off valves 4, 5, use is preferably made of ball valves with a 90° rotation of the spindle between the open and closed positions. As safety valves 6, 7, use is advantageously made of a valve type with a cone abutting against a seat in connection with the respective outlet. When the pressure in the tank is too high, the cone rises from the seat and emits gas via its outlet tube.
Valves suitable for use in this context are supplied by the Swedish company Armaturjonsson AB, viz. a full-flow ball valve of the AJ 3665 type, and a safety valve of the AJ 4545L type.
Between the two valve assemblies 4, 6 and 5, 7 there is connected a device according to the invention, generally designated 8, for alternately controlling the two cooperating ball valves 4 and 5. According to a first embodiment, the control device 8 comprises a connection tube 9 whose ends are connected with the valve body of the ball valves 4, 5, and a lever 10 for manually operating the ball valves 4, 5 in a manner which will be described in more detail below. For better clarity, the control device 8 and the two ball valves 4, 5 are indicated by thick lines in Fig. 1, whereas the remaining parts are indicated by thin lines.
In the normal state, the two ball valves 4, 5 should be open (Figs 1 and 3), implying that the two safety valves 6 and 7 communicate with the pressure vessel 1 and thus are in their active position. By means of the control device 8, it should further be possible to put the ball valves 4, 5 in two different service positions, viz. a first position in which the first ball valve 4 is open while the second ball valve 5 is closed (Fig. 2), and a second position in which the first ball valve 4 is closed while the second ball valve 5 is open. When reversing the ball valves between the service positions, it must not happen that both ball valves 4, 5 are fully or partly closed. If the safety valve 6 is to be dismounted for inspection, the ball valve 4 is closed by means of the control device 8 by pivoting the lever 10. This movement should not affect the ball valve 5 which should be fully open when closing the ball valve 4. Of course, this also applies when the safety valve 7 is to be dismounted.
The control device 8 according to the invention is described in more detail in Figs 2 and 3. The two ball valves 4, 5 comprise in prior-art manner a valve spindle 11, 12 which is nonrotatably connected with a valve member 13, 14 pertaining thereto and having a passage 15, 16. The two spindles 11, 12 are directed towards one another and the spindle ends define a space in which a carrier element 17 is arranged. The carrier element 17 is connected to the end portion of the lever 10 by means of a threaded pin 18. Further the carrier element 17 comprises a first coupling means in the form of a cam 19 for engaging a matching coupling means in the form of a groove 20 in the free end of the first spindle 11. The opposite side of the carrier element 17 is formed with a second coupling cam 21 for engaging a matching groove 22 in the end of the second spindle 12. In the normal state (Fig. 3), both ball valves 4, 5 are open and the carrier element 17 can be moved into coupling engagement with the respective spindle end by means of the lever 10.
Now supposing that the safety valve 7 is to be dismounted. The lever 10 is then moved in the direction of the second spindle 12 (arrow A) until the cam 21 of the carrier element 17 engages the groove 22 in the end of the spindle 12. Subsequently the lever 10 is pivoted in the direction of arrow B to the position illustrated in Fig. 2. During these movements, the lever 10 is guided by means of the pin 18 in a guiding slot generally designated 23 which will be described in more detail below. The closing of the ball valve 5 thus does not affect the open ball valve 4. Of course the same applies to the closing of the ball valve 4, i.e. the open ball valve 5 is not affected.
The guiding slot 23 formed in the tube 9 comprises an axial portion 24 for axially guiding the lever 10 and, thus, the carrier element 17 when moving from the normal position (open valves 4, 5) to one of the service positions. Thus the carrier element 17 is movable between two end positions between the spindle ends. In each end position, the axial slot portion 24 passes into a slot portion 25, 26 extending partially in the circumferential direction of the tube 9. By means of the partially circumferential slot portions 25, 26 the guiding operation is ensured when pivoting the lever 10 in either direction to rotate the carrier element 17 while engaging one spindle end.
By this guiding operation, the carrier element 17 can be axially moved from the normal position (open valves 4, 5) into coupling engagement with one of the spindles 11, 12, but cannot in the service position be moved into coupling engagement with the spindle associated with the valve which in this position is open. Thus, it is ensured that at least one of the ball valves 4, 5 is continuously fully open, at the same time as a state, in which both ball valves 4, 5 are fully or partly closed, is prevented. According to an embodiment not shown, the partially circumferential portions 25, 26 instead extend in the same direction, which means that the guiding slot 23 is U-shaped. The lever 10 is then pivoted in the same direction for both service positions.
Figs 4-5 illustrate a control device according to a second embodiment of the invention. In this variant, the lever 10 is fixedly connected with a tube member 27 which is axially slidable on the spindles 11, 12 and in which the carrier element 17 is fixedly mounted. The tube member 27 is slidable a distance corresponding to the length of the space between the spindle ends. In this case, the guiding operation is effected by means of slots formed in the outside of the spindles 11, 12 and adapted to cooperate with inwardly directed, fixed projections on the inside of the tube member 27. More precisely, each spindle is formed with an axial slot 28 and a slot 29 extending partially in the circumferential direction of the spindle and passing, in the end position, into the axial slot 28. An inwardly directed projection 30 inside the tube member 27 cooperates with these guiding slots 28, 29. When operating the ball valve 5, the tube member 27 is moved in the direction of arrow C by means of the lever 10, the projection 30 following the axial slot 28 until the carrier element 17 has been moved into coupling engagement with the spindle end. In the subsequent turning motion for closing the associated valve, the projection 30 follows the circumferential slot 29. The same applies to the operation of the spindle 11. According to a variant which is not illustrated, the spindles are instead fitted with projections for cooperation with internal guiding slots in the tube member.
Figs 6-7 illustrate a control device according to a third embodiment of the invention, in which the flexibility of the mutual positioning of the valves 4, 5 is fully developed. The connection tube 9 which is used in the first embodiment may here be said to be cut in the middle (two tube portions 9a and 9b) in order to facilitate optional mounting of the valves 4, 5. Thus, the valves 4, 5 may be arranged on completely different levels, and the spindles 11, 12 need not be axially directed towards one another.
To accomplish the required guiding of the carrier element 17 use is made of an elongate, flexible member in the form of a wire 31 which is connected to each valve 4, 5, more precisely to each spindle 11, 12. The carrier element 17 is a tube member 32 which is fixedly connected with the lever 10 and slipped over and freely movable along the wire 31 between the spindles 11, 12. The tube member 32 is formed with internal keys and grooves, i.e. splines, for engagement with matching external keys and grooves, or splines, formed on the two spindles 11, 12. These splines thus correspond to the coupling means according to the first two embodiments, as described above. In other respects, the control device according to the third embodiment functions completely analogously to the first embodiments. The tube portions 9a, 9b are formed with slots corresponding to the above-described guiding slots 24-26.
The control device according to the invention preferably is fitted with locking means for locking the lever 10 in the different positions, thereby preventing the valves 4, 5 from being tampered with. Fig. 6 illustrates this locking function in more detail. In order to lock the lever 10 in the position illustrated in Fig. 6, a pin 33 is inserted through a hole in the tube portion 9a and into a recess 34 in the tube member 32 (see Fig. 7). Then the pin 33 is connected with a fixed mounting 35 on the tube portion 9a by means of an ordinary padlock 36. Similar locking facilities are of course to be found on the other tube portion 9b.
In Fig. 7, both valves 4, 5 are open. If in this position one wants to prevent somebody from trying to close one of the valves 4, 5, both pins 33 are inserted in the respective tube portion 9a, 9b and are secured by padlocks 36. The pins 33 then prevent engagement between the carrier element 17 and the spindles 11, 12.
It should be observed that the control device can be provided with elastic protective sleeves (not shown) which in the first embodiment cover the guiding slot (Fig. 2) and which in the second embodiment cover the joint between each tube end and spindle (Fig. 4). If required, protective sleeves can of course also be used in the third embodiment (Figs 6-7).
The control device according to the first embodiment of the invention is readily adjustable to different distances between the two outlets on the pressure vessel in that the length of the connection tube between the shut-off valves is adapted thereto. An improved possibility of optional mutual positioning and alignment of the valves is, of course, achieved by means of the control device according to the third embodiment of the invention. There the orientation of the valve spindles can be almost fully optional. When needed, the spindles can be fitted with extension members which at their free end comprise engaging means or longitudinal splines. In this specification, the term "spindle" includes such extension members.
Finally, it should also be emphasised that the invention is not limited to the embodiments described above, but several modifications are conceivable within the scope of the inventive idea as presented in the appended claims. The shut-off valves may be some other type of valve, e.g. throttle valves which are moved through 1/4 of a turn between the open and closed positions. Moreover, the means for coupling engagement between the carrier element and the spindle ends, as well as the guiding operation can be accomplished in other ways. The important thing is that coupling engagement with and rotating of one spindle is carried out, without the other spindle being affected. It should also be emphasised that the lever in the second embodiment can be replaced by a turning tool, for example a spanner, which is moved into engagement with an external recess on the tube for axial movement and, respectively, rotation thereof.

Claims

Device for alternately controlling two cooperating valves (4, 5) for switching between different states, viz. a first state in which the first valve is open and the second is closed, and a second state in which the first valve is closed and the second is open, each valve (4, 5) having a valve member (13, 14) which is rotatable between an open and a closed state by means of a spindle (11, 12), characterised in that one end of each valve spindle (11, 12) is nonrotatably connected with the valve member (13, 14), while the other end is free, and that said valves (4, 5) can be set to a third state, in which both valves are open, by means of a lever-operated carrier element (17) having a first coupling means (19) which is movable, by means of said lever (10), into engagement with a matching coupling means (20) in the free end of the first spindle (11) for rotating the same and the associated valve member (13) by means of the lever, without the second spindle (12) being affected, and having a second coupling means (21) which is movable, by means of said lever, into engagement with a matching coupling means (22) in the free end of the second spindle (12) for rotating the same and the associated valve member (14) by means of the lever, without the first spindle (11) being affected, said device further having means (9, 18, 23; 27-30; 31-32) for guiding the carrier element (17) in such a manner that this is movable by means of said lever (10) from said third state, in which the valves are open, into coupling engagement with one of the spindles (11, 12) but, in the first or second state, is prevented from being moved into coupling engagement with the spindle pertaining to the valve which in this state is open, thereby preventing a state in which both valves (4, 5) are fully or partly closed.
Device according to claim 1, wherein the two spindles (11, 12) are directed axially towards one another and their free ends define between themselves a space in which the carrier element (17) is axially movable by means of said lever (10) between the coupling engagements with the respective spindle end during guiding of a surrounding tube (9; 27) which contains said carrier element (17) and into which the opposed spindles (11, 12) are inserted from each end of said tube.
Device according to claim 2, wherein the tube (9) extends between said valves (4, 5) and is fixedly connected at each end with the respective valve, and that said tube (9) in the area of said space between the spindle ends is formed with an open guiding slot (23) in which an end portion (18) of said lever (10) is positioned and connected with said carrier element (17) for lever operation of the movements thereof between the coupling engagements with the spindle ends and while being guided in the slot (23).
Device according to claim 3, wherein the guiding slot (23) comprises an axial portion (24) within which said carrier element (17) is axially movable by means of said lever (10) between the coupling engagements with the respective spindle end corresponding to two end positions of said lever, and two portions (25, 26) partially extending in the circumferential direction of said tube (9) which are located in said two end positions and within each of which said carrier element (17) engages the respective spindle end and is rotatable by pivoting said lever (10) for opening and closing the associated valve, and wherein the two circumferential slot portions (25, 26) pass into the axial slot portion (24) in each end position.
Device according to claim 2, wherein said lever (10) is connected with said tube (27) which consequently is axially slidable on the spindles (11, 12) a distance corresponding to the length of said space between the spindle ends and in which the carrier element (17) is fixedly mounted, and wherein the outside of said spindles (11, 12) is fitted with guide means (28, 29) for cooperation with matching guide means (30) on the inside of said tube (27) for lever operation of the carrier element (17) between the coupling engagements with said spindles.
Device according to claim 5, wherein the guide means of each spindle (11, 12) comprise an axial slot (28) for axial guiding of said tube (27) and, thus, said carrier element (17) between the coupling engagements with the respective spindle end corresponding to two end positions of said lever (10), and a slot (29) partially extending in the circumferential direction of the spindle (12) and adapted to guide said tube (27), when the carrier element (17) engages the spindle end for rotation by pivoting said lever (10), wherein the guide means of said tube (27) comprises an inwardly directed projection (30) which engages and follows the guiding slots (28, 29) of the associated spindle (12), and wherein said circumferential slot (29) passes into the axial slot (28) in the end position.
Device according to claim 1, wherein said means for guiding the carrier element (17) comprise an elongate, flexible member (31), preferably a wire, which is connected with each valve (4, 5) and on which the carrier element (17) is arranged so as to be freely movable between the valve spindles (11, 12).
Device according to claim 7, wherein said carrier element (17) is a tube member (32) fixedly connected with said lever (10) and having internal keys and grooves, i.e. splines, which form said coupling means of the carrier element (17) and are adapted to engage matching external keys and grooves, i.e. splines, on each valve spindle (11, 12) which form the coupling means thereof, and wherein the tube member (32) is slipped over and freely movable along said flexible member (31).
Device according to claim 7 or 8, wherein each valve (4, 5) has a tube portion (9a, 9b) surrounding the associated spindle (11, 12) and formed with slots for guiding the movements of said lever (10).
Device according to any one of the preceding claims, wherein locking means (33-36) are arranged for locking said lever (10) in the three positions, thereby preventing the valves (4, 5) from being tampered with.